This invention relates generally to component feeding systems, and more particularly to carrier tape-based component feeding systems used in conjunction with surface-mount or equivalent automated assembly systems.
A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.
The present invention is directed to an improvement of tape or component feeders used in printed circuit assembly technology in which electronic components are placed at precise locations on the surface of a printed circuit board. As illustrated by the Hover-Davis MPF and QP2F products, component tape feeders are used for sequentially feeding surface-mount components to a host assembly system. The host system typically includes a pick-and-place machine having an automated or robotic head for retrieving the component from the component feeder and placing the component on the surface of a printed circuit board that is being assembled.
For ease of delivery and handling, components are often stored in a carrier tape as depicted in Prior Art FIG. 10. Carrier tape 30, consists of a flexible base or component tape layer 32 of paper, metal or plastic having pockets 34 at regular intervals along its length. Carried within each pocket is one component 36 to be placed on the printed circuit board. The components 36 are secured within their respective pockets using a thin, generally transparent material 40, commonly referred to as xe2x80x9ccover tapexe2x80x9d or xe2x80x9ccover layerxe2x80x9d that extends the length of the carrier tape, and is generally slightly wider than the pockets that it covers. The cover tape is typically fastened to the carrier tape with a pressure or temperature activated adhesive along each of its two longitudinal edges. The carrier tape may also include a plurality of through-holes 42 spaced at a predefined pitch, wherein a drive mechanism is able to engage the holes and advance the tape at a controlled rate/distance in order to accurately present the components to the pick-up location.
In component tape feeders, such as the Hover-Davis models noted above, a tape feeder advances the carrier tape to position a pocket, and therefore a component within the pocket, at a predetermined pick-up point, where the host pick and place machine is able to retrieve the component for placement on the printed circuit board. As the carrier tape is advanced off of a supply reel, the cover tape is typically pulled or peeled back from the carrier tape and wound upon a cover tape take-up reel, thereby exposing the pocket 34 and the component 36 before it reaches the pick-up point.
A long-standing problem with this technology has been the disposition of the cover tape. Two main methods are in use for dealing with the problem. The first is to wind the cover tape on a take-up reel located above and behind the pick point.
Examples of patents in which this solution is employed include U.S. Pat. Nos. 4,327,482; 4,735,341; and 5,299,902, the teachings of which are hereby incorporated by reference. A problem with this method is that in order for the cover tape take-up reel to be reused, the cover tape has to be manually removed therefrom. In addition, the cover tape must initially be threaded, or otherwise attached, to the take-up reel for the winding of the cover tape around the reel to occur. This is often accomplished with adhesive tape or similar product, however, attachment requires that a sufficient quantity of the cover tape be available to reach the take-up reel and attach thereto. Furthermore, the take-up reel requires not only time, but also that an adhesive tape (e.g., masking or splicing tape) be readily available when cinching a new take-up reel for the carrier tape.
A second method of handling the cover tape after it is peeled back from the carrier tape involves using a pair of pinch rollers to push the cover tape into a reservoir. U.S. Pat. No. 5,725,140 to Weber et al., also incorporated herein by reference, discloses this method. While such a system resolves the take-up reel problem, it still requires separate mechanisms for driving/pulling and disposal of the cover tape, and the cover tape must still be started with a measure of the cover tape being routed through the feeder to the pinch rollers and through the pinch rollers each and every time a new reel of component tape is started or restarted in the feeder.
Another method is disclosed in U.S. Pat. No. 4,586,670, which is also incorporated herein by reference. In this method, two pinch rollers are also used, however, instead of pushing the cover tape into a bin, the cover tape is allowed to drop into a waste receptacle. The problem with this method is that it increases the width of the feeder, which means fewer feeders can service a single host pick and place machine. In addition, the cover tape, which is very thin and generally made of a plastic material, often accumulates a static charge and may stick to the feeder or other surfaces after it has been cut or chopped.
The present invention solves the various problems described above by avoiding the complete separation of the carrier tape layers (component tape and the cover tape or cover layer)xe2x80x94thereby allowing the disposal of the component tape to accomplish disposal of the cover tape as well. More specifically, the cover tape is parted along one edge, or slit in the middle for wider component tapes. The cover tape flap(s) created by the parting operation are then retracted or folded back away from the region above the component, whereby the component is exposed for retrieval at the pick-up location. Subsequent to the pick-up location, the carrier tape with the parted cover tape flap(s) still attached thereto, is then directed to a waste receptacle or similar disposal mechanism, eliminating the need for a cover tape take-up reel.
In accordance with the present invention, there is provided a component feeding apparatus for supplying components to an automated assembly system, said system using a component feeding means having a length of carrier tape with a plurality of regularly spaced pockets in the component tape, each pocket holding a component therein, and a cover tape thereover to retain the components within each pocket until the component approaches a pick-up location, the apparatus comprising: means for parting the cover tape so as to partially expose the component while keeping at least one edge of said cover tape affixed to the component tape; and a channel for guiding a cover tape flap around the pick-up location, whereby the component is completely exposed and the cover tape flap will not interfere with retrieval of the component at the pick-up location. In accordance with an alternative embodiment of the above-described invention, said parting means may include a heating element for applying heat to the cover tape along the edge to be parted.
In accordance with another aspect of the present invention, there is provided a component feeder for supplying electronic components to an automated assembly system for assembling printed circuit boards, said system using a component feeding means having a length of carrier tape with a plurality of regularly spaced pockets in a component tape, each pocket holding a component therein, and a cover tape thereover to hold the components within each pocket until the component approaches a pick-up location, comprising: a means for separating a single edge of a cover tape from the component tape and folding said cover tape along a line adjacent to a second edge at least about 90 degrees from the plane of said component tape; and means for maintaining said cover tape in retracted condition as said component tape passes a pick-up location where successive pockets in said component tape are exposed, such that a pick and place machine may have access to any electrical components located in a pocket located at said pick-up location.
In accordance with yet another aspect of the present invention, there is provided, in a component feeding apparatus for supplying components to an automated system for assembling printed circuit boards, said system using a component feeding means having a length of carrier tape, the carrier tape including a plurality of regularly spaced pockets in a component tape, each pocket holding a component therein, and a cover tape thereover to retain the components within each pocket until the component approaches a pick-up location, a method of presenting components for retrieval at the pick-up location, comprising the steps of: in advance of the pick-up location, parting the cover tape so as to create a cover tape flap and partially expose the component while keeping at least one edge of said cover tape affixed to the component carrier tape; and while feeding the component carrier tape, guiding the cover tape flap around the pick-up location, whereby the component is completely exposed and the cover tape flap will not interfere with retrieval of the component at the pick-up location.
The techniques described above are advantageous because they simplify the component feeders used with printed circuit assembly operations. By eliminating the need to separately handle the carrier and cover tape members, the component feeding process is simplified (e.g., fewer cover tape handling devices are employed) and made more reliable. Moreover, once the waste cover tape disposition problem is appropriately addressed, the cost of operation of carrier tape feeding systems will be reduced and the operation of the assembly system can proceed uninterrupted for longer periods of time.
The techniques of the present invention are advantageous because they provide a range of alternative parting techniques, each of which is useful in appropriate situations (e.g., component tape width). A wide variety of component feeding operations can be implemented using these techniques. Each technique can ensure that the component tape (carrier and cover) are fed to the pick-up location without separating the cover tape from the carrier tape, thereby simplifying disposal of the component tape. As a result of the invention, the maintenance of a component tape feeding system is significantly improved.